<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        body {
            height: 100vh;
            display: flex;
            flex-direction: column;
        }

        header,
        footer {
            height: 15vh;
            background-color: #ccc;
        }

        main {
            flex: 1;
            background-color: aquamarine;
        }

        main {
            display: flex;
        }
        aside{
                width: 150px;
                background-color: green;
        }
        article{
                flex: 1;
        }
        aside,article{
               height: 100%;
        }
    </style>
</head>

<body>
    <header>header</header>
    <main>
        <aside></aside>
        <article>
            .....
        </article>
        <aside></aside>
    </main>
    <footer>footer</footer>
</body>

</html>